Pouliot made his appearance at the midget level for the Moose Jaw Warriors Midget AAA of the SMAAAHL in 2008–09 with a short, five-game stint,[1] though he still qualified to play in bantam at the time. A highly regarded prospect, Pouliot was taken at the 1st overall pick in the 2009 WHL Bantam Draft by the Portland Winterhawks,[2] who placed him on their protected list. Pouliot then rejoined Moose Jaw for the full season in 2009–10, finishing as a point-per-game player (14 goals, 29 assists).[3] Pouliot finished fourth on his team in scoring and as the top-scoring defenceman. During the course of the season, Pouliot found time to play for the Winterhawks, first in January and again after the Warriors were eliminated,[4] recording a single assist in seven games, as he played against players who were three to four years his senior.

Pouliot joined the Winterhawks for the 2010–11 season. On a team laden with talent (2010 4th- and 5th-overall picks Ryan Johansen and Nino Niederreiter along with future first-round picks in 2011Sven Bärtschi and Joe Morrow), Pouliot played the majority of the season and finished with 30 points in 66 games.[5] During the season, Pouliot was invited to play for Canada-West at the 2011 World U-17 Hockey Challenge, finishing with three assists in five games as Canada-West lost in the fifth-place game to Canada-Atlantic.[6] Portland finished the regular season with 103 points in the standings, finishing one point ahead of U.S. Division rival Spokane to clinch the top spot in the Western Conference.[7]

In an opening-round sweep of the Everett Silvertips, Pouliot scored a goal in the Game 2 7–2 rout, his only point of the series. Following a win in the conference semifinals against the B.C. Division champion Kelowna, the Winterhawks lost 4–1 to the Kootenay Ice. Pouliot posted an assist in each of Portland's first two games in the series, including a helper on Ty Rattie's overtime power play game-winner in Game 1. While Portland had a successful post-season, Pouliot's 4 points in 21 games were considered disappointing after a regular season in which he had averaged a half-point per game. Over the summer, Pouliot was a member of Canada's gold-medal team at the 2011 Ivan Hlinka Memorial Tournament.

Pouliot entered his draft year with a 4-assist night in only his second game of the season[8] and while his output dipped as the season went along, he was performing much better in his second full season with the Winterhawks. Despite being left off Canada's roster for the 2012 World Junior Ice Hockey Championships, Pouliot was listed in the top 10 of North American skaters by NHL Central Scouting in the mid-season rankings though, once again, not as the best defenceman.[9] Pouliot finished the season with 59 points, almost doubling his output from the season before, while playing in all 72 of Portland's games. The Winterhawks again had a stellar season, ending up as the most prolific offensive team in the WHL, due in part to Pouliot's scoring prowess.

Portland swept their opening round playoff series against the Kelowna Rockets, in which Pouliot produced 2 assists, and beat the Kamloops Blazers to move on to the conference finals versus the Tri-City Americans, a matchup which pitted the top offensive and defensive teams in the WHL against one another. In another four-game sweep of the Americans, Pouliot put up a 4-assist performance in Game 2, assisting on each of the Winterhawks' goals except the overtime game-winner.[10] In their second consecutive finals appearance, the Winterhawks were matched up against the Edmonton Oil Kings, who finished the regular season with the best record in the league. Portland lost the series in seven games, and Pouliot, who had been effective in the first five games of the series, was silent in the last two, including being on the ice for two of Edmonton's goals in Game 7.[11]

Despite the outcome, Pouliot produced 17 points in 22 games during the playoffs. The final Central Scouting rankings placed him as the #12-ranked North American skater.[12] The draft host Pittsburgh Penguins took Pouliot with the 8th overall selection that they had obtained from Carolina in the Jordan Staal trade[13] when Pittsburgh had their own first-round selection at 22nd overall.[14] Less than a week later, Pouliot was invited to Canada's National Development Camp,[15] the first stepping stone in joining the 2013 WJC roster. A few months later, Pouliot signed a 3-year entry-level contract with Pittsburgh[16] just a few days before the 2012 NHL Lockout was to begin.[17]

With the departure of fellow Penguins draft pick Joe Morrow to the AHL, Pouliot became the Winterhawks' star offensive defenceman and immediately rose to the challenge. Pouliot took charge of the power play and increased his scoring. By the end of November, Pouliot had posted 24 points in 26 games, including 5- and 6-game point streaks, earning him an invitation to Canada's WJC selection Camp with fellow Penguins prospect Scott Harrington.[18] However, after the second day of the camp, Pouliot was returned to Portland.[19] Upon his return to the WHL, Pouliot immediately produced a 3-assist game and finished with 12 points in the month of December.

In the third game back in January, Pouliot suffered a high ankle sprain (unreported at the time), and would miss time intermittently over the next few months.[20] Nevertheless, he finished the regular season with 45 points in 44 games. Portland finished with the best record in the WHL (57-12-1-2) along with the top offense in the league and the best defence in the conference.[21] In a five game opening series win over the Everett Silvertips, Pouliot finished with 9 points[22] (6 coming on the power play) as well as assisting on the game-winner in the deciding match.[23]

In a second round sweep of the Spokane Chiefs, the Winterhawks scored 18 goals and allowed only 3, and Pouliot recorded a 4-point night in the opening match.[24] A win over the Kamloops Blazers in the conference finals propelled the Winterhawks into the WHL finals for the third straight season. Portland won in six games, during which Pouliot posted four assists, finishing the playoffs with 20 points in 21 games to lead all defencemen in postseason scoring.[25]

On October 21, 2014, Pouliot was assigned to the Wilkes-Barre/Scranton Penguins of the AHL by the Pittsburgh Penguins.[27] On December 20, 2014, during a rash of injuries to the Penguins defensemen, Pouliot was recalled for the first time in his career subsequently he made his NHL debut and scored his first NHL goal on his first shot against Roberto Luongo of the Florida Panthers.[28][29]